發(fā)動機原理及詳解之_往復式發(fā)動機

1、發(fā)動機原理及詳解之-往復式發(fā)動機A reciprocating engine consists of (1) compression of air or pre-compressed air (or air-fuel mixture in the case of certain types of engines) within the cylinder of the engine by the action of a piston, (2) addition of heat energy into the compressed air by directly combusting the fu

2、el in the compressed air, followed by (3) expansion of the hot pressurized combustion products in the cylinder against the piston connected to the load to produce useful work. The auto engine and the diesel engine are examples of a reciprocating engine. The compression ratio of an auto engine is low

3、er and the combustion process is initiated by a spark plug while in a diesel engine, the compression ratio is significantly higher and the fuel is ignited by the heat of compression.Spark Ignition Engines. Next, there are two types of spark ignition engines: the four stroke cycle and the two stroke

4、cycle. In the four stroke engine, four strokes of the piston are required to complete a cycle: (1) intake stroke where the piston moves with the intake valve open and the exhaust valve closed such that a mixture of air with atomized and vaporized fuel is taken into the cylinder, (2) compression stro

5、ke, in which the air/fuel mixture is compressed with both valves closed followed by ignition of the air/ fuel charge by a timed spark, (3) power or expansion stroke with both valves closed, and finally (4) the exhaust stroke in which the pistons moves with the exhaust valve open and thus completing

6、the cycle. The cylinder walls are cooled by circulating a cooling medium through the cylinder jackets or by incorporating fins cooled by air.In the two stroke engine, the intake and exhaust strokes are eliminated by using pre-compressed intake charge to displace the exhaust gases. The two stroke eng

7、ine has the advantage of a high power to weight ratio because the engine has a power stroke each revolution. This advantage, however, is offset by the loss of a portion of the intake charge with the exhaust gases, resulting in lower efficiencies. The two stroke engine has thus limited applications s

8、uch as in small boat engines, lawnmower engines where low cost and weight are more important than efficiency.Compression Ignition Engines. With a sufficiently high compression ratio and a suitable fuel, autoignition occurs in a reciprocating engine. The engine is similar to the spark ignited engines

9、 described above except that during the compression stroke, only air is taken into the piston and compressed to ignition conditions and then, the fuel is atomized directly into the combustion chamber at a controlled rate.【中文注解】往復式發(fā)動機由以下幾部分組成（1）由于活塞運動，氣缸內(nèi)生產(chǎn)的壓縮空氣或預壓縮的空氣（或者因某些發(fā)動機類型不一樣，也可能是空氣燃油混合物）；（）在氣

10、缸內(nèi)的壓縮空氣中直接燃燒燃油，增加壓縮空氣所帶的熱能，然后（）氣缸中的高溫高壓混和氣體推動活塞連桿做有用功，汽車發(fā)動機及柴油發(fā)動機全是這種發(fā)動機的代表。汽油發(fā)動機的壓縮比要低一些，而氣體燃燒是靠火花塞點火實現(xiàn)的，而柴油發(fā)動機的壓縮比顯然要高得多，它是靠壓縮生熱而燃燒的。點燃式發(fā)動機點燃式發(fā)動機可以分為兩種類型，一種是四沖程發(fā)動機，另一種是兩沖程發(fā)動機。對于四沖程發(fā)動機，一個循環(huán)包括四個步驟：（1）進氣沖程（2）壓縮沖程；（3）燃燒膨脹沖程；（4）排氣沖程。 兩沖程發(fā)動機內(nèi)，進氣沖程與排氣沖程都省略了，因為進入氣缸的預壓混和氣體將要排出的廢氣取代，它擁有較高動力重量比，因為每圈發(fā)動機都

11、會產(chǎn)生做一次膨脹沖程，而這個優(yōu)勢是以一部分燃氣進入氣缸時隨尾氣排出被浪費了造成的，因此它的效率很低，用途極為有限。壓燃式發(fā)動機這種發(fā)動機與點燃式發(fā)動機相似，但是在壓縮沖程中，僅有空氣進入并被壓縮達到燃燒條件，然后氣霧化了的燃油按控制的速率噴入燃燒室。In the two stroke engine, the intake and exhaust strokes are eliminated by using pre-compressed intake charge to displace the exhaust gases. The two stroke engine has the adva

12、ntage of a high power to weight ratio because the engine has a power stroke each revolution. This advantage, however, is offset by the loss of a portion of the intake charge with the exhaust gases, resulting in lower efficiencies. The two stroke engine has thus limited applications such as in small

13、boat engines, lawnmower engines where low cost and weight are more important than efficiency.Compression Ignition Engines. With a sufficiently high compression ratio and a suitable fuel, autoignition occurs in a reciprocating engine. The engine is similar to the spark ignited engines described above

14、 except that during the compression stroke, only air is taken into the piston and compressed to ignition conditions and then, the fuel is atomized directly into the combustion chamber at a controlled rate.【中文注解】往復式發(fā)動機由以下幾部分組成（1）由于活塞運動，氣缸內(nèi)生產(chǎn)的壓縮空氣或預壓縮的空氣（或者因某些發(fā)動機類型不一樣，也可能是空氣燃油混合物）；（）在氣缸內(nèi)的壓縮空氣中直接燃燒燃油，增加壓縮空氣所帶的熱能，然后（）氣缸中的高溫高壓混和氣體推動活塞連桿做有用功，汽車發(fā)動機及柴油發(fā)動機全是這種發(fā)動機的代表。汽油發(fā)動機的壓縮比要低一些，而氣體燃燒是靠火花塞點火實現(xiàn)的，而柴油發(fā)動機的壓縮比顯然要高得多，它是靠壓縮生熱而燃燒的。點燃式發(fā)動機點燃式發(fā)動機可以分為兩種類型，一種是四沖程發(fā)動機，另一種是兩沖程發(fā)動機。對于四沖程發(fā)動機，一個循環(huán)包括四個步